Compensation for graphical image display system for compensating the particular non-linear characteristic of a display

ABSTRACT

A display system is provided for displaying graphical images on a radiant energy-responsive surface, such as that of a cathode ray tube, with a radiant energy beam which is displaced to a plurality of different image positions on the surface under the control of a position storage means for registering various digital representations respectively representative of a plurality of image positions. A compensating signal supply serves to supply various compensating digital representations which are respectively representative of the compensation required at the various image positions. Depending on the digital representations in the position storage means, the signal supply is controlled to provide a particular coded pattern of compensating digital signals. These compensating digital signals are then converted into analog compensating signals for compensating for a particular non-linear characteristic of the display system.

United States Patent Horvath 4 1 Jan.30,1973

COMPENSATION FOR GRAPHICAL Primary Examiner-Benjamin R. Padgett Assistant ExaminerJ. M. Potenza AttrneyYount and Tarolli DISPLAY [57] ABSTRACT 7 :RbtM.HthClld, l 51 Inventor z g orva eve an A display system provided for displaying graphical images on a radiant energy-responsive surface, such as [73] Assignee: Harris-Intertype Corporation, that of a cathode ray tube, with a radiant energy beam Cleveland,0hio which is displaced to a plurality of different image [22] Filed: Oct. 7,1970 positions on the surface under the control of a position storage means for reglstering various digital [2i] Appl. No.: 78,655 representations respectively representative of a plurality of image positions. A compensating signal supply serves to supply various compensating digital [2%] :JSCCII representations which are respectively representative [.It. 3. of the compensation required at the various image Fleld OI Search 2 7 G positions. Depending on the representations in the position storage means, the signal supply is con- [561 References C'ted trolled to provide a particular coded pattern of com- UNITED STATES PATENTS pensating digital signals. These compensating digital signals are then converted into analog compensating 3,3l9,ll2 5/1967 Annus etal ..3l5/27 GD signals for compensating for a particular non-linear 3,435,278 3/1969 Carlock et al. ..3l5/26 X characteristic of the display system, 3,566,18l 2/1971 Figlewicz ..3l5/27 GD 3,237,048 2/1966 Slavik ..3t5/22 17 Claims, 2 Drawing Figures CONTROL HORIZOVDIL r- 6 L/A/E' AORIZMML l/Ok/ZflA/ML VERTICAL FOCUS 09065880,? ACCUMUMIW BINARY T01 DEFLECHM .57 5 3/25 0 005 OF/V L/A/E 0/005 0/005 0/005 MATE/x I 056005,? MAfQ/X MATR/X MA TR/X 1 5 03/ 0 22 2 26 Hoe/mm l/MlZflA/IAL x/ae/mviu Veer/rm SCALE ommaw 5725 8/26 Fww 0/4 0/4 l HORIZGWML H awe/tars? i r--"' me/20mm #5277014 y; son/.6 scnur 0/4 0/4 VERTICAL SCALE 44 v me/2m VL-wflau Va M467?! CHAREE? t 0 l 0/4 VERTICAL cHARAcrER 40 i rm/mum r 0- LEAD/N6 4 R 30 -s- MAav/e 32 l RULE 437535;" vw

PATENTEUJM 30 1975 SHEET 10F 2 COMPENSATION FOR GRAPHICAL IMAGE DISPLAY SYSTEM FOR COMPENSATING 'IIIE PARTICULAR NON-LINEAR CHARACTERISTIC OF A DISPLAY This invention relates to the art of graphical image display systems and, more particularly, to compensating for non-linear response characteristics thereof.

The invention is particularly applicable for use in conjunction with compensating for non-linear response characteristics of a cathode ray tube used for forming graphical displays on the tubes face. However, it is to be appreciated that the invention has broader applications and may, for example, be used to compensate for non-linear response characteristics for other display apparatus, such as where the beam is generated by a laser mechanism.

Reference is made to the following related US. patent applications, the disclosures of which are hereby incorporated by reference. These applications include Ser. No. 591,734, filed Nov. 3, 1966, entitled TYPESETTING SYSTEM; Ser. No. 710,350, filed Mar. 4, l968, entitled PI-IOTOTYPESETTING AP- PARATUS; Ser. No. 710,351, filed Mar. 4, 1968, entitled POINT SIZE COMPUTATIONS AND EXPO- SURE CONTROL DEVICE FOR PHOTO- TYPESETTING APPARATUS; and Ser. No. 1,124, filed Jan. 7, 1970, entitled COMPENSATION SYSTEMS FOR CATHODE RAY TUBE DISPLAY SYSTEMS, all assigned to the assignee of the present application.

One application of the present invention is in conjunction with phototypesetting wherein a cathode ray tube is employed to display images in the form of characters on the tubes face, and these characters are then photographed for purposes of setting type. Consequently, it is desirable in such a system that characters formed on the face of the cathode ray tube be accurately positioned and precisely defined independently of any non-linear response characteristic of the cathode ray tube.

It is well known, for example, that the voltage required to deflect the electron beam of a cathode ray tube is not a linear function of the position of the visual spot produced on the screen itself. Consequently, it is desirable to compensate for such non-linearity in the spacing of visual spots.

In addition to the above-mentioned positioning inaccuracies resulting form the non-linear response characteristics of a cathode ray tube, the spot formed on thetubes face will blur as a result of focus variations as a spot is formed at different locations across the face of the tube. Hence, it is also desirable that compensation be made to correct for non-linear beam focus characteristics.

The present invention is directed to apparatus for compensating for these non-linear response characteristics at various positions along a radiant energyresponsive surface. The invention contemplates a display system which serves to display graphical images on a radiant energy-responsive surface, such as the face of a cathode ray tube, with a radiant energy beam which is displaced to different positions on the surface under the control of a position storage means registering digital representations respectively representative of the different positions.

O interrogation signal, providing a coded pattern of compensating digital signals for the particular position represented by the interrogation signal. An interrogating circuit, such as a decoding circuit, serves to provide interrogation signals respectively in dependence upon the digital representations in the position storage means for application to the compensating signal supply means to obtain therefrom a particular coded pattern of compensating digital signals. These compensating digital signals are then converted by a digital-toanalog converting means so as to provide for each of the image positions an analog compensating signal having a magnitude dependent on the coded pattern of compensating digital signals for the image position.

Still further in accordance with the present invention, the compensating signal supply means exhibits non-destructive readout characteristics so that interrogation signals applied thereto do not destroy the stored information.

Still further in accordance with the present invention, the compensating signal supply means includes a diode matrix having removable diodes, together with switching means for simulating the diodes for use in empirically determining the compensating digital representations required for each of the image positions.

The primary object of the present invention is to compensate for non-linear beam response characteristics in a display system which displays graphical images on a radiant energy-responsive surface with a radiant energy beam.

A still further object of the present invention is to provide a signal supply meansfor supplying digital representations of compensating signals for each image position, and wherein the supply means exhibits nondestructive readout characteristics so that rewrite circuitry is not required to maintain the information being stored.

A still further object of the present invention is to provide a compensating signal supply means including a diode matrix having removable diodes to thereby facilitate'programming of information.

A still further object of the present invention is to provide switching means for the diode matrix for purposes of simulating diodes therein to empirically determine the compensating digital representations required for each of the image positions.

The forgoing and other objects and advantages of the invention will be more readily appreciated from the following description of the preferred embodiment of the invention taken in conjunction with the accompanying drawings which are part thereof and wherein:

FIG. 1 is a combined block diagram-schematic illustration of one application of the invention; and

FIG. 2 is a schematic illustration of a portion of a diode matrix used in conjunction with the invention.

GENERAL DESCRIPTION Referring now to the drawings wherein the showings are for purposes of illustrating the preferred embodiment of the invention only and not for purposes of limiting same; FIG. 1 generally illustrates a display system including a cathode ray tube CRT having a face on which images are formed with a radiant energy beam. The beam is displaced along face 10 to various image positions 1 through N at which graphical images, such as characters, are to be formed. The beam is positioned to positions 1 through N under the control of a position storage means in the form of horizontal accumulator HA which registers digital representations 1 through N respectively representative of positions 1 through N. The image positions 1 through N are represented by the six most significant digits stored in the accumulator and interpolation is bad between these positions dependent upon the least significant digits stored in the accumulator. The six mos't significant digits are decoded by means of a six line binary to one of N line decoder I so that one of the decoders output circuits 1 through N is energized in dependence upon the status of the accumulator HA. Decoder I and its output circuits 1 through N serve as an addressing or interrogating means for addressing or interrogating compensation signal supplying or storage means CS which includes four diode matrices, l2, l4, l6 and 18. Each of these diode matrices serves to store N compensating digital representations respectively representative of the compensation required at each of the positions 1 through N on tube face 10 to compensate for the non-linear response characteristics of the tube. Each matrix has addressable input circuits respectively connected to output circuits 1 through N of decoder I and a plurality of output circuits which are connected to the input of a digital-to-analog converter. The output circuits of each diode matrix serves, upon receipt of an interrogation signal from decoder I, to provide a coded pattern of compensating digital signals for the associated one of the N positions on tube face 10. Digitalto-analog converters 20, 22, 24 and 26 receive the compensating digital signals from matrices 12, 14, 16 and 18, respectively, to provide analog compensating signals having magnitudes dependent upon the particular coded pattern of compensating digital signals applied to the input circuits of the digital-to-analog converters. The output signals of digital-to-analog converters 20 through 26 are applied to various circuits, to be described in greater detail hereinafter, for compensating for the non-linear characteristics of tube 10. Having briefly described the invention, reference is now made to the detailed description presented below.

CONTROL PROCESSOR AND REGISTERS As briefly described hereinbefore, the horizontal accumulator HA controls the positioning of the beam on the face 10 of cathode ray tube CRT under the control of a control processor CP. The control processor may take various forms, such as that described in detail in the aforementioned applications and specifically in ap' plication Ser. No. 710,350, and provides digital signals for purposes of controlling the horizontal position at which characters are to be formed, character size, the formation of characters along lines parallel to both the horizontal and vertical co-ordinate axes of tube face 10, as well as such additional functions particularly applicable for phototypesetting including leading control and rule control. The digital signals provided by the control processor CI for controlling these functions are routed to both the horizontal accumulator HA as well as additional digital registers. Briefly, these registers, as shown in FIG. 1, include a horizontal scale register HS, a horizontal character register HC, a vertical scale register VS, a vertical character register VC, a leading register L and a rule register R. As the names imply, these registers serve to control different functions in forming characters on tube face 10, and in the recording of the characters on associated film for use in phototypesetting operations.

The horizontal and vertical character registers HC and VC receive information from the control processor CP for incrementally positioning the beam along lines parallel to the horizontal and vertical axes to form desired images or characters at each of the image positions 1 through N on tube face 10. At each position at which a spot is to be formed on tube face 10, the control processor CI unblanks the radiant energy beam, and this is illustrated in FIG. 1 by an output circuit taken from control processor C? to a blank-unblank terminal Z. As described in the afore-mentioned applications, the control processor CP may include optical or magnetic storage memories which store digital representations of plotting instructions for forming various characters which, in turn, are selected by information received from a suitable control tape.

The point size or character size of each character is dependent on the distance between adjacent spots formed on tube face 10. Thus, if it is desired to increase the distance between adjacent spots in the horizontal or vertical directions, then digital information representative of such changes is applied from the control processor to the horizontal and vertical scale registers HS and VS, respectively. By utilizing two registers, it is possible to vary the vertical and horizontal sizes independently of each other.

As graphical images or characters are formed at each of the positions 1 through N, the tube face 10, may be recorded on a photographic film (not shown) for use in phototypesetting. Coarse leading control of the film with respect to the tube face 10 may be achieved by conventional mechanical leading control systems which move the film in incremental vertical steps upon suitable commands. In addition to mechanical leading, the afore-mentioned applications also disclose that the vertical position of the beam may be adjusted to obtain fine electronic leading control of the beam. The leading register L, shown in FIG. 1, stores digital representations obtained from the control processor CP for controlling the electronic leading functions.

It is also desirable, particularly in phototypesetting, to provide rule lines or reference lines on tube face 10. As discussed in the afore-mentioned applications, these rule lines may be generated by placing an electronic beam on tube face 10 such that a number of closely spaced parallel lines are formed. As shown in FIG. 1, rule register R serves to receive digital signals from control processor CP for controlling this function.

ANALOG-TO-DIG ITAL CONVERTERS The output circuits of the registers discussed thus far are applied to associated digital-to-analog converters for obtaining analog signals to be applied to various control terminals of the cathode ray tube CRT. Basically, each analog-to-digital converter has an input circuit for receiving digital signals, an input circuit for receiving a reference signal, and an output circuit which provides an analog output signal having a value which is a fractional part of the reference signal dependent upon the particular pattern of digital signals received. A suitable digital-to-analog converter for use herein may be that as shown in afore-mentioned U.S. application Ser. No. 710,350. That converter includes a plurality of switching elements, such as transistors, that are activated in accordance with the digital switching signals. The digital input signals are received from an associated register and the switching of the switching elements controls the amount of current that flows through a plurality of summing resistors into a summing input terminal of an operational summing amplifier. The output of the summing amplifier is proportional to a fractional part of the reference signal as determined by the applied digital signals.

As shown in FIG. 1, the output circuits representing the most significant digits of the horizontal accumulator I-IA are applied to the input of a major horizontal linear digital-to-analog converter 30 having its reference signal taken from a 8+ voltage supply source. The status of the horizontal accumulator determines which of the major image positions 1 through N will be in effect. The analog output signal from the digital-toanalog converter 30 is applied through a summing resistor 32 to the inverting input circuit of a current summing operational amplifier 34 having a feedback resistance 36. The amplified signal from amplifier 34 is applied to appropriate circuitry, represented by the terminal, X on tube CRT, for deflecting the beam in accordance with the magnitude of the signal received from amplifier 34. Dependent on the particular image position 1 through N in effect, additional positioning of the beam is provided due to the analog output signal obtained from the horizontal deflection digital-toanalog converter and which is applied through a summing resistor 38 to the inverting input circuit of amplifier 34. Further positioning of the beam is obtained by interpolating between image positions as discussed in the afore-mentioned application Ser. No. 710,3 50. This interpolation is accomplished with an interpolation digital-to-analog converter 40 having its input circuit connected to receive digital signals representative of the status of the least significant digits stored in the accumulator HA and to receive a reference signal from the horizontal size digital-toanalog converter 22. The analog output signal from the interpolation digital-to-analog 40 is applied through another summing resistor 42 and thence to the inverting input circuit of operational amplifier 34.

Character generation is obtained with the use of a horizontal character digital-to-analog converter 44 and a horizontal scale digital-to-analog converter 46 which respectively receive digital signals from the horizontal character register HC and the horizontal scale register HS. The reference signal for the horizontal scale converter is obtained from the analog output signal of the horizontal size digital-to-analog converter 22. The reference signal for the horizontal character converter 44 is, in turn, obtained from the analog output signal of the horizontal scale converter 46. The analog signal of converter 44 is applied through another summing re sistor 48 and thence to the inverting input circuit of operational amplifier 34.

The digital signals stored by the vertical character register VC are applied to the input of a vertical character digital to analog converter 50 having its analog output signal applied through a summing resistor 52 to the inverting input circuit of an operational summing amplifier 54 having a feedback resistor 56. The output signal from amplifier 54 is applied to suitable Y axis deflection circuitry represented by the terminal Y on tube 10 to deflect the electronic beam along the Y axis in accordance with the magnitude of the deflection signal. As described in the afore-mentioned U.S. application Ser. No. 710,350, the reference signal for the vertical character digital-to-analog converter 50 is obtained from a vertical scale digital-toanalog converter 58 which receives digital signals from the vertical scale register VS and reference signals from the vertical size digital to analog converter 24.

The digital signals stored by the leading register L are applied to the leading digital-to-analog converter 60 which receives its reference signals from the vertical size digital-to-analog converter 24. The output analog signals from the leading digital-to-analog converter 60 are applied through another summing resistor 62 to the inverting input circuit of operational amplifier 54. Similarly, the digital signals stored by the rule register R are applied to a rule digital-to-analog converter 64 which receives its reference signals from the vertical size digital-to-analog converter 24. The analog output signals of the rule digital analog converter 64 are applied through another summing resistor 66 and thence to the inverting input circuit of operational amplifier 54. Tube CRT is also provided with a focusing control, represented in FIG. 1 by the terminal F, which receives analog control signals from the focus digital-to-analog converter 26 as amplified by amplifier 70.

COMPENSATION SIGNAL CONTROL In accordance with the present invention, the analog output signals of the digital-to-analog converters 20, 22, 24 and 26 are controlled in magnitude dependent upon the particular image position 1 through N in effect. This is obtained by storing digital representations in each of the matrices l2, 14, 16 and 18, representative of the compensation required at each of the image positions 1 through N. Preferably, each matrix 12, 14, 16 and 18 serves a quick access memory having several word lines for storing digital representations which, when a word line is interrogated, provides a pattern of digital signals. Although various types of memories may be used for storing these digital representations, it is preferred that each memory take the form of a quick access read only memory; that is, a readout cycle should be nondestructive and, hence, a separate rewrite circuit need not be employed. Each of the digits may be stored with various binary storage means. In the preferred embodiment, however, the digital representations are stored with the use of diodes.

Reference is now made to FIG. 2 which illustrates a portion 12' of diode matrix 12, it being understood that matrices 14, I6 and 18 are constructed in the same fashion. As shown in FIG. 2, matrix portion 12' includes a plurality of horizontally extending word line conductors 70, 72 and 74, respectively, extending from representative output circuits 1, 2 and N of the decoder I. Also, vertically extending bit line conductors 76, 78, 80 and 82 are provided and which terminate in output circuits 0, b, c, and d, respectively. The word line conductors and bit line conductors cross each other, as shown in FIG. 2, but are not electrically connected to each other. Bit line conductors 76, 78, 80 and 82, respectively, extend through equally weighted resistors 84, 86, 88 and 90 to ground. The digital representations stored by matrix portion 12' are obtained with the use of diodes connected between the word line conductors and the bit line conductors. For example, diode 92, poled as shown in FIG. 2, is connected from word line conductor 70 to bit line conductor 80. Another diode 94 is shown as being connected from word line conductor 72 to bit line conductor 76. Also, diodes 96 and 98 are shown as being connected from word line conductor 74 to bit line conductors 78 and 82, respectively. These diode locations are shown merely as an example for discussion herein. Diode 92 is representative of a stored binary l signal, since a positive signal applied on output circuit 1 of decoder I to word line conductor 70 will result in a positive signal appearing on output circuit of matrix portion 12'. Since diode 92 is the only diode connecting word line conductor 70 with one of the bit line conductors, then the pattern of output signals in digital form which are obtained when a positive signal is applied to word line 70 is 0010. Similarly, when a positive signal is applied to word line conductor 72, the pattern of digital signals obtained from the output circuits is 1000. Also in the illustration give, when a positive signal is applied to word line conductor 74, the pattern of digital signals is 0101.

The compensation word" or digital pattern of signals provided by each word line is determined empirically. As an aid in the determination, convenience switches 100, I02, 104 and 106 are respectively connected from bit line conductors 76, 78, 80 and 82 through a resistor 108 to a 8+ voltage supply source. Each of these switches is shown as a simple switch; however, it is to be appreciated that other switches, such as transistors, may be used. If the binary pattern for a particular image position, say image position number 2, is being determined empirically, then the various switches 100, 102, 104 and 106 are operated until an operator notes that the correct compensation has been made in beam deflection or focus, as viewed on the face of the cathode ray tube. This visual observation may indicate that the correct compensation has been obtained only when switch 100 is closed. Consequently, the correct compensation for position 2 may be represented by the digital pattern 1000. This is indicative that diode 94 should be inserted from word line conductor 72 to bit line conductor 76.

To facilitate the programming of matrix portion 12', the diodes are preferably removably secured to the matrix as opposed to being permanently fixed, as by soldering. This is illustrated in FIG. 2 by diode 108 having conductive prongs 110 and 112 which may be plugged into suitable conductive apertures 1 l4 and 116 which are respectively provided in electrical connection with word line conductor 72 and bit line conductor 80. It is to be appreciated that the showing of diode 108 is by way of example only and is meant to be a simplified illustration of a plugboard diode. The use of such plugboard diodes permits easy programming of the digital word information, as well as visual indications as to the information being stored in the matrix.

OPERATION Each of the diode matrices 12, 14, 16 and 18 is programmed to store the proper compensation required at each of the image positions 1 through N. Consequently, depending on the status of the most significant digits of the horizontal accumulator HA, the beam is positioned to a particular position on the tube face 10 dependent on the magnitude of the analog signal obtained from the major horizontal linear digital-to-analog converter 30. The magnitude of this signal is linearly related to the digital representations of the six most significant digits in the horizontal accumulator and, hence, does not provide compensation for non-linear beam response characteristics of the tube. Depending on the particular position in effect, one of the output circuits 1 through N of the decoder I is energized to interrogate a particular word line in each of the matrices 12, 14, 16 and 18. With matrix 12 being interrogated a particular pattern of digital signals representative of the compensation to be made at the image position is provided on the output circuits of the matrix. These digital signals are then converted by the horizontal deflection digitalto-analog converter 20 and the analog signal obtained therefrom is applied through amplifier 34 to effect further positioning of the beam on face 10. This analog signal obtained from digital-to-analog converter 20 is linearly related to the digital representations stored in the interrogated word line of matrix 12. However, since the digital representations stored in matrix 12 are empirically chosen the analog signal is non-linear with respect to the digital representations of the six most significant digits in the horizontal accumulator HA. The foregoing compensation is effective at each of the image positions 1 through N in the manner described above.

At any particular image position 1 through N, the output signal taken from the digital-to-analog converter 22 will have a particular value dependent on the digital representations in the word line being interrogated in matrix 14. This analog signal is applied as a reference signal to the horizontal scale digital-toanalog converter 46, as well as to the interpolation digital-to-analog converter 40. Converter 40 provides an analog output signal to obtain further positioning of the beam on tube face 10 having a magnitude which is a fractional part of the reference signal dependent on the digital signals applied to the converter from the portion of the horizontal accumulator HA representing the least significant digits. Consequently, at each of the positions 1 through N the beam is coarsely positioned due to the signal obtained from converter 30 and then repositioned to compensate for non-linear beam response characteristics by the output signal obtained from converter 20 and then further positioning for interpolation purposes is obtained with the output signal obtained from converter 40.

The size of a character generated at a particular position 1 through N is determined by the output signals obtained from digital-to-analog converter 46 and applied as a reference to the horizontal character digitalto-analog converter 44. The output signal of converter 46 has a magnitude which is a fractional part of the output signal of converter 22 in dependence upon the digital signals applied to converter 46 from the horizontal scale register HS. The deflection signal itself is obtained from the horizontal character digital-to-analog converter and that signal has a magnitude which is a fractional part of the reference signal obtained from converter 46 in dependence upon the digital signals applied to the converter from the horizontal character register HC. The output signal obtained from converter 44 is amplified by amplifier 34 and applied to the horizontal deflection circuitry represented by terminal X on tube CRT. Consequently, at each of the image positions 1 through N compensation is made for the horizontal size of the character to be formed.

The vertical size digital-to-analog converter 24 serves a purpose similar to converter 22 and provides an analog signal for each image position 1 through N having a value dependent upon the digital representations stored in the word line being interrogated. This signal is applied as a reference signal to the vertical scale digital-to-analog converter 58, as well as to the leading digital-to-analog converter 60 and the rule digital-to-analog converter 64. The output signal of the vertical scale digital-to-analog converter 58 has a magnitude which controls the vertical size of a character to be generated. This signal is proportional to the reference signal obtained from converter 24 dependent on the digital signals applied to the converter from the vertical scale register VS. The output signal taken from the converter 58 is applied as a reference signal to the vertical character digital-to-analog converter 50. Consequently, the output signal from converter 50 is of a magnitude which is a fractional part of the reference signal from converter 58 dependent upon the digital signals applied to the converter from the vertical character register VC. Thus, for eachimage position 1 through N the magnitude of vertical deflection signals applied to the vertical deflection circuitry, represented by the terminal Y in FlG. l, is controlled dependent on the compensation signals stored in the vertical size diode matrix 16.

The leading function is obtained by applying a signal to the deflection control circuitry Y and is obtained from the leading digital-to-analog converter 60. This signal has a magnitude which is a fractional portion of the analog signal obtained from the digital-to-analog converter 24 in dependence upon the digital signals applied to converter 60 from the leading register L. Similarly, the rule function is obtained by applying a signal to the vertical deflection circuitry Y and this signal is obtained from rule digital-to-analog converter 64. This signal has a magnitude which is a fractional part of the output signal obtained from the digital-toanalog converter 24 in dependence upon the digital signals applied to converter 64 from the rule register R.

The focus control is represented by the terminal F on tube CRT in FIG. 1. The focus of the beam is controlled in accordance with the beam position throughout image positions 1 through N. The focus signal is obtained from the focus digital-to-analog converter 26. The magnitude of this signal is dependent upon the digital signals provided by the interrogated word line in matrix 18 for a particular one of the image positions 1 through N. Thus, at each image position 1 through N one of the word lines in matrix 18 is interrogated to obtain a particular pattern of digital signals representative of the focus compensating signal required so that the beam focus will remain constant at various beam positions across the tube face 10.

The invention has been described with reference to a preferred embodiment; however, it is to be appreciated the invention is not limited to the same, as various modifications may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Having described my invention,

lclaim:

1. In a display system for displaying graphical images on a radiant energy-responsive surface with a radiant energy beam which is displaced to N different image positions on said surface under the control of a position storage means registering N digital representations respectively representative of said N positions; the im-' provement for compensating for non-linear beam response characteristics at said N positions and comprising:

compensating means having N compensating digital representations respectively representative of the compensation required at said N positions and having output circuit means for, in response to one of N interrogation signals each representative of one-of said N positions, providing a coded pattern of compensating digital signals for said one of N positions;

interrogating means for providing said N interrogation signals respectively in dependence upon the digital representations of said position storage means for application to said compensating signal storage means to obtain therefrom a particular said coded pattern of compensating digital signals; and

digital-to-analog converting means for providing for each of said N positions, an analog compensating signal having a magnitude dependent on the particular coded pattern of compensating digital signals.

2. In a display system as set forth in claim 1, 'wherein said interrogating means includes N output circuits which are respectively energized to carry a said interrogation signal dependent upon the digital representations of said position storage means.

3. In a display system as set forth in claim 2, wherein said compensating means includes N input circuits for respectively receiving interrogation signals from said N output circuits.

4. In a display system as set forth in claim 3, wherein the output circuit means of said compensating means includes a plurality of compensating output circuits for carrying a said coded pattern of compensating digital signals. a

5. In a display system as set forth in claim 1, wherein said compensating means exhibits nondestructive readout characteristics in that said interrogation signals do not destroy the stored information.

6. In a display system as set forth in claim 5, wherein said compensating means includes a diode decoding matrix.

7. In a display system as set forth in claim 6, wherein said matrix includes removable diodes and switching means for simulating said diodes for empirically determining the compensating digital representations required for each of said N positions.

8. In a cathode ray tube display system in which nonlinear responses of the cathode ray tube detract from the quality of the display on the screen of the cathode ray tube wherein the display system is of the type in which a position storage means stores information as to the position of the electron beam on the screen of the cathode ray tube, the improvement comprising compensating means having a plurality of selectively addressable digital code means each having a programmable circuit means for providing a particular programmed digital code representing a compensation to be provided for an associated beam position, means for selectively addressing one of said digital code means in dependence upon the position information stored by said storage means so that its programmable circuit means provides a said particular programmed digital code, and a digital-to-analog converting means which produces a compensating analog output signal dependent upon the selected said particular programmed digital code which is appropriate for compensating for a particular non-linear response of said cathode ray tube.

9. In a cathode ray tube display system as set forth in claim 8 having focus control means and wherein said compensating means is a focus compensating means and means for applying said analog compensation signal to said said focus control means.

10. In a cathode ray tube display system as set forth in claim 8 wherein said compensating means is a horizontal size compensating means is a horizontal size compensating means and means for applying said analog compensation signal as a reference signal to a horizontal scale digital-to-analog converting means.

11. In a cathode ray tube display system as set forth in claim 8 wherein said compensating means is a vertical size compensating means and means for applying said analog compensation signal as a reference signal to a vertical scale digital-to-analog converting means.

12. In a cathode ray tube display system as set forth in claim 8 wherein said compensating means is a vertical size compensating means and means for applying said analog compensation signal as a reference signal to a leading analog-to-digital converting means.

13. In a cathode ray tube display system as set forth in claim 8 wherein said compensating means is a vertical size compensating means and means for applying said analog compensation signal as a reference signal to a rule analog-to-digital converting means.

14. A display system for displaying graphical images on a radiant energy surface with a radiant energy beam comprising position storage means for sequentially registering different digital representations respectively representative of different image positions on said surface, beam deflection means for deflecting said beam to said positions including signal supplying means comprising a plurality of programmable circuit means for providing respective deflection signals correspondin o respective ones of said digital representations for e fecting non-linear deflections in response to said digital representations to compensate for non-linear beam response characteristics, said programmable circuit means comprising means operable to individually change the magnitude of selected ones of said deflection signals.

15. A display system as set forth in claim 14 wherein said programmable circuit means comprises a plurality of addressable elements.

16. A display system for displaying graphical images on a radiant energy surface with a radiant energy beam comprising positions storage means for sequentially registering different digital representations respectively representative of different image positions on said surface, beam deflection means for deflecting said beam to said positions comprising a plurality of programmable signal supplying means for respectively supplying programmed signals to effect non-linear deflections of said beam in dependence upon said digital representations stored by said position storage means for effecting a said non-linear beam deflection for the image position represented by a said digital representation, whereby for each of said image positions a non-linear beam deflection is provided to compensate for nonlinear beam response characteristics, and means for selectively programming said signal supplying means for changing the said programmed signals to effect different non-linear beam deflections at said image positions.

17. A display system as set forth in claim 16 wherein said plurality of programmable signal supplying means are addressable, and means for selectively addressing said signal supplying means in dependence upon said digital representations stored by said position storage means to obtain from a selected said signal supplying means a specific said programmed signal. 

1. In a display system for displaying graphical images on a radiant energy-responsive surface with a radiant energy beam which is displaced to N different image positions on said surface under the control of a position storage means registering N digital representations respectively representative of said N positions; the improvement for compensating for non-linear beam response characteristics at said N positions and comprising: compensating means having N compensating digital representations respectively representative of the compensation required at said N positions and having output circuit means for, in response to one of N interrogation signals each representative of one of said N positions, providing a coded pattern of compensating digital signals for said one of N positions; interrogating means for providing said N interrogation signals respectively in dependence upon the digital representations of said position storage means for application to said compensating signal storage means to obtain therefrom a particular said coded pattern of compensating digital signals; and digital-to-analog converting means for providing for each of said N positions, an analog compensating signal having a magnitude dependent on the particular coded pattern of compensating digital signals.
 1. In a display system for displaying graphical images on a radiant energy-responsive surface with a radiant energy beam which is displaced to N different image positions on said surface under the control of a position storage means registering N digital representations respectively representative of said N positions; the improvement for compensating for non-linear beam response characteristics at said N positions and comprising: compensating means having N compensating digital representations respectively representative of the compensation required at said N positions and having output circuit means for, in response to one of N interrogation signals each representative of one of said N positions, providing a coded pattern of compensating digital signals for said one of N positions; interrogating means for providing said N interrogation signals respectively in dependence upon the digital representations of said position storage means for application to said compensating signal storage means to obtain therefrom a particular said coded pattern of compensating digital signals; and digital-to-analog converting means for providing for each of said N positions, an analog compensating signal having a magnitude dependent on the particular coded pattern of compensating digital signals.
 2. In a display system as set forth in claim 1, wherein said interrogating means includes N output circuits which are respectively energized to carry a said interrogation signal dependent upon the digital representations of said position storage means.
 3. In a display system as set forth in claim 2, wherein said compensating means includes N input circuits for respectively receiving interrogation signals from said N output circuits.
 4. In a display system as set forth in claim 3, wherein the output circuit means of said compensating means includes a plurality of compensating output circuits for carrying a said coded pattern of compensating digital signals.
 5. In a display system as set forth in claim 1, wherein said compensating means exhibits nondestructive readout characteristics in that said interrogation signals do not destroy the stored information.
 6. In a display system as set forth in claim 5, wherein said compensating means includes a diode decoding matrix.
 7. In a display system as set forth in claim 6, wherein said matrix includes removable diodes and switching means for simulating said diodes for empirically determining the compensating digital representations required for each of said N positions.
 8. In a cathode ray tube display system in which non-linear responses of the cathode ray tube detract from the quality of the display on the screen of the cathode ray tube wherein the display system is of the type in which a position storage means stores information as to the position of the electron beam on the screen of the cathode ray tube, the improvement comprising compensating means having a plurality of selectively addressable digital code means each having a programmable circuit means for providing a particular programmed digital code representing a compensation to be provided for an associated beam position, means for selectively addressing one of said digital code means in dependence upon the position information stored by said storage means so that its programmable circuit means provides a said particular programmed digital code, and a digital-to-analog converting means which produces a compensating analog output signal dependent upon the selected said particular programmed digital code which is appropriate for compensating for a particular non-linear response of said cathode ray tube.
 9. In a cathode ray tube display system as set forth in claim 8 having focus control means and wherein said compensating means is a focus compensating means and means for applying said analog compensation signal to said said focus control means.
 10. In a cathode ray tube display system as set forth in claim 8 wherein said compensating means is a horizontal size compensating means is a horizontal size compensating means and means for applying said analog compensation signal as a reference signal to a horizontal scale digital-to-analog converting means.
 11. In a cathode ray tube display system as set forth in claim 8 wherein said compensating means is a vertical size compensating means and means for applying said analog compensation signal as a reference signal to a vertical scale digital-to-analog converting means.
 12. In a cathode ray tube display system as set forth in claim 8 wherein said compensating means is a vertical size compensating means and means for applying said analog compensation signal as a reference signal to a leading analog-to-digital converting means.
 13. In a cathode ray tube display system as set forth in claim 8 wherein said compensating means is a vertical size compensating means and means for applying said analog compensation signal as a reference signal to a rule analog-to-digital converting means.
 14. A display system for displaying graphical images on a radiant energy surface with a radiant energy beam comprising position storage means for sequentially registering different digital representations respectively representative of different image positions on said surface, beam deflection means for deflecting said beam to said positions including signal supplying means comprising a plurality of programmable circuit means for providing respective deflection signals corresponding to respective ones of said digital representations for effecting non-linear deflections in response to said digital representations to compensate for non-linear beam response characteristics, said programmable circuit means comprising means operable to individually change the magnitude of selected ones of said deflection signals.
 15. A display system as set forth in claim 14 wherein said programmable circuit means comprises a plurality of addressable elements.
 16. A display system for displaying graphical images on a radiant energy surface with a radiant energy beam comprising positions storage means for sequentially registering different digital representations respectively representative of different image positions on said surface, beam deflection means for deflecting said beam to said positions comprising a plurality of programmable signal supplying means for respectively supplying programmed signals to effect non-linear deflections of said beam in dependence upon said digital representations stored by said position storage means for effecting a said non-linear beam deflection for the image position represented by a said digital representation, whereby for each of said image positions a non-linear beam deflection is provided to compensate for non-linear beam response characteristics, and means for selectively programming said signal supplying means for changing the said programmed signals to effect different non-linear beam deflections at said image positions. 